It seems to me people are starting to confuse terms Whaling and Spending your cores.
Whaling - you used money to buy the cores. Spending cores that you gained through playing the game (scouting, unlocking map tiles and event rewards) is anything but whaling. Its a grind, its hard earned, its playing the game.
Thus bying a bundle of the event currency with such cores is not whaling.
Just though I throw this out there since some people seemed a bit confused at times.

As for me, I can clear all tiles, but requires a downtime after one boss tile for the tanks to repairs, since the usual is that around half my tanks repairing. Defense buff and Attack buff commander abilities work overtime for me in this event.